Organic Thin Film Transistor Applications Research Articles

Arbitrary Density of States in an Organic Thin-Film Field-Effect Transistor Model and Application to Pentacene Devices

We present a modular numerical model for organic thin-film field-effect transistors (OTFTs) that allows for an arbitrary density of states to be independently defined for the semiconductor bulk and the semiconductor surface next to the gate insulator. We can derive the surface charge density dependence on the interface field as well as the space-charge-limited current characteristics. Together with a model of the contacts, we arrive at a physical model that is applied to a series of OTFTs in staggered inverted (top contact) geometry with various gate insulator treatments

Influence of silanol groups on the electrical performance of organic thin-film transistorsutilizing organosiloxane-based organic–inorganic hybrid dielectrics

A solution-processable organosiloxane-based organic–inorganic hybrid gate dielectric layerfor application in organic thin-film transistors has been synthesized by a sol–gel process. Inthe sol–gel derived hybrid film, owing to an incomplete condensation reaction, silanolgroups serve as functional groups of the inorganic siloxane backbone. In order to investigatethe influence of the silanol groups on the electrical performance of transistors withorganosiloxane-based dielectrics, transistors employing hybrid dielectrics with differentamounts of the silanol group were prepared and electrical performance parameters such asoff-current, threshold voltage, field-effect mobility, and hysteresis were analysed.

A hybrid mask–mould lithography scheme and its application in nanoscale organic thin filmtransistors

Nanoimprint lithography (NIL) has stimulated great interest in both academic research andindustrial development due to its high resolution, high throughput and low costadvantages. Though NIL has been demonstrated to be very successful in replicatingnanoscale features, it also has its limitations as a general lithography technique. Itsfundamental moulding characteristics (i.e. physically displacing polymer materials)frequently lead to pattern defects when replicating arbitrary patterns, especially patternswith broad size distribution. To solve this problem, we have developed a combinednanoimprint and photolithography technique that uses a hybrid mould to achieve goodpattern definitions. In this work, we applied this technique to fabricate finger-shapednanoelectrodes, and demonstrated nanoscale pentacene organic thin film transistors(OTFTs). Methods of the hybrid mask–mould (HMM) fabrication and resultson the device electrical characteristics are provided. With combined advantagesof both photolithography and NIL, and the applicability to general nanoscaledevice and system fabrication, this method can become a valuable choice for lowcost mass production of micro- and nanoscale structures, devices and systems.

Clustering of Pentacene and Functionalized Pentacene Ions in a Matrix-Assisted Laser Desorption/Ionization Orthogonal TOF Mass Spectrometer

A high-performance orthogonal time-of flight (TOF) mass spectrometer, in combination with the matrix assisted laser desorption/ionization (MALDI) source operating at elevated pressure ( approximately 1 torr in N(2)), was used to perform MALDI-TOF analyses of pentacene and some of its derivatives with and without an added matrix. These molecules are among the most interesting semiconductor materials for organic thin film transistor applications (OTFT). The observation of ion-molecule reactions between "cold" analyte ions and neutral analyte molecules in the gas phase has provided some insight into the mechanism of pentacene cluster formation and its functionalized derivatives. Furthermore, some of the matrices employed to assist the desorption/ionization process of these compounds were observed to influence the outcome via ion-molecule reactions of analyte ions and matrix molecules in the gas phase. The stability and reactivity of the compounds and their clusters in the MALDI plume during gas-phase expansion were evaluated; possible structures of the resulting clusters are discussed. The MALDI-TOF technique was also helpful in distinguishing between two isomeric forms of bis-[(triisopropylsilyl)-ethynyl]-pentacene.

Chemical and biological sensors based on organic thin-film transistors

The application of organic thin-film transistors (OTFTs) to chemical and biological sensing is reviewed. This review covers transistors that are based on the modulation of current through thin organic semiconducting films, and includes both field-effect and electrochemical transistors. The advantages of using OTFTs as sensors (including high sensitivity and selectivity) are described, and results are presented for sensing analytes in both gaseous and aqueous environments. The primary emphasis is on the major developments in the field of OTFT sensing over the last 5-10 years, but some earlier work is discussed briefly to provide a foundation.

Substituted Indolo[3,2-b]Carbazoles: A New Class of Stable, High Mobility Organic Semiconductors for Thin Film Transistors

AbstractProperly functionalized indolo[3,2-b]carbazoles represent a new class of stable, high-mobility organic semiconductors for organic thin-film transistor applications. Both 5,11-disubstituted and peripherally substituted indolo[3,2-b]carbazoles with proper substituents self-organized into highly crystalline terrace-layered structures under suitable processing conditions. Organic TFTs using channel semiconductors of this nature exhibited excellent field-effect transistor properties, with mobility to 0.14 cm2 V-1 s-1 and current on/off ratio to 107. By virtue of their relatively low HOMO levels and large band gaps, this class of semiconductors also displayed excellent environmental stability under ambient conditions, an appealing characteristic for organic TFT applications.

Poly(3,3‘ ‘-dialkylterthiophene)s: Room-Temperature, Solution-Processed, High-Mobility Semiconductors for Organic Thin-Film Transistors

Most solution-processed organic semiconductors for organic thin film transistor applications require high-temperature annealing and/or fabrication in an inert atmosphere to achieve high mobility. Solution-processed poly(3,3‘ ‘-dialkylterthiophene) 3 was found to provide functionally useful transistor properties even when fabricated at room temperature under ambient conditions.

Indolo[3,2-b]carbazole-Based Thin-Film Transistors with High Mobility and Stability

Proper functionalization of indolo[3,2-b]carbazole led to a new class of high-performance organic semiconductors suitable for organic thin-film transistor (OTFT) applications. While 5,11-diaryl-substituted indolo[3,2-b]carbazoles without long alkyl side chains provided amorphous thin films upon vacuum deposition, those with sufficiently long alkyl side chains such as 5,11-bis(4-octylphenyl)indolo[3,2-b]carbazole self-organized readily into highly crystalline layered structures under similar conditions. OTFTs using channel semiconductors of this nature exhibited excellent field-effect properties, with mobility up to 0.12 cm(2) V(-1) s(-1) and current on/off ratio to 10(7). As this class of organic semiconductors has relatively low HOMO levels and large band gaps, they also displayed good environmental stability even with prolonged exposure to amber light, an appealing characteristic for OTFT applications.

An Orientation‐Controlled Pentacene Film Aligned by Photoaligned Polyimide for Organic Thin‐Film Transistor Applications

AbstractWe have demonstrated that the photoalignment method could be used to control the structural anisotropy of pentacene films, an active semiconducting layer, in thin‐film transistors (TFTs) with conspicuously anisotropic electrical characteristics. The photoaligned pentacene films were characterized with respect to structure and morphology using X‐ray diffraction and atomic force microscopy. Compared to the pentacene films that are not controlled, a maximal 25‐times increase in field‐effect mobility (up to 0.75 cm V–1 s–1) has been achieved in the photoaligned pentacene‐based TFTs by aligning pentacene orientation parallel to the direction of current flow with the help of a photoaligned polyimide layer. Mobility anisotropic ratio in the range of 2.7–8.3 for the current flow parallel and perpendicular to the alignment of the photoaligned pentacene films have been observed for photoaligned pentacene‐based TFTs.

Organic thin film transistors: from active materials to novel applications

In this paper, a bird's eye view of most of the organic materials employed as n-channel and p-channel transistor active layers is given along with the relevant device performances; organic thin film transistors (OTFT) operation regimes are discussed and an interesting perspective application of OTFT as multi-parameter gas sensor is proposed.